Pneumatic staple driving guns



Sept. 9, 1958 L. R. CAMPBELL ETAL PNEUMATIC STAPLE DRIVING GUNS Z SheetS-Sheet 1 Filed July 12, 1955 /Y M/////// f m L. R. CAMPBELL ETAL 2,850,738

PNEUMATIC STAPLE DRIVING GUNS Sept. 9, 1958 2 Sheets-Sheet 2 Filed July 12, 1955 I a I 1 I I I I I I n I WM Inak 'ATI'OI/VIY United States Patent 2,850,738 PNEUMATIC STAPLE DRIVING GUNS Lee R. Campbell, Royal Oak, Alton Schoening, Detroit, and Le Roy C. Reiterman, Warren, Mich., assignors to Kenwood Industrial Development Company, Inc., Dearbom,-Mich., a corporation of Michigan 7 Application July 12,1955, Serial No. 521,455 15 Claims. (Cl. 1-44.41

This invention relates to a pneumatic staple driving gun and has for its principal object to improve upon the construction of the gun described in U. S. Patent 2,713,165. I

As disclosed in the prior patent, the pneumatic staple driving gun consists of a power unit in the form of a handle, having a cylinder associated therewith, in which is slidably mounted a piston that-actuates a staple driver which detaches the staples one by one from a strip of interconnected staples housed in 'a magazine which in turn is provided with staple feeding means for urging the strip of interconnected staples into the path of movement of the staple driver to cause the detached staplesto be driven into the material or materials to be stapled. The handle or power unit as disclosed in said prior patent is suitably connected to a source of air under pressure and is provided with an expansion chamber, a

valve chamber and suitable conduits leading to the cylinder; trigger actuated valve means being interposed between the valve chamber and said conduits to control the admission of the air under pressure to the cylinder.

The power .unit of this application, like that of said prior patent, is adapted to be used interchangeably with any one of a plurality of magazine unit assemblies designed for staples of various sizes and adapted to be quickly and easily secured to the power unit.

Each of the magazine unit assemblies of the prior patent includes, in addition to the magazine and feed structure for storing and feeding the staples to the staple driver, a bumper retainer in which a bumper of resilient material is enclosed, a nose piece in which the lower end of the staple driver is slidably mounted, the staple driver having an enlarged head at its upper end for engagement by the piston mounted in the air cylinder of the power unit; and a piston return spring, for normally urging the piston to the top of the cylinder, is associated with the bumper retainer and partially compressed between said bumper retainer and an adapter provided with screw threads for engagement with cooperating screw threads in the air cylinder, together with means for engaging the driver andholding it in a lowered position with the piston spring partially compressed, the pressure of the partially compressed piston spring being employed to hold the parts, that make up the magazine unit assembly, in assembled condition. Thus, when the magazine unit assembly is not being used with a power unit, the magazine assembly may be readily stored in a tool crib and removed from the crib for use with a power unit as desired.

The principal object of the present invention is to improve upon the construction shown in the said prior patent by simplifying the structure of the power unit and, by eliminating the bumper retainer, reducing the number of parts thereof, and in making certain specific changes in some of the constituent parts, which result in consequent savings in manufacturing and assembling costs, as well as contributing materially to a more efiicient functioning of the stapling gun.

2,850,738 Patented Sept. 9, 1953 The above and other objects of the present invention .will appear more fully from the following more detailed description and by reference to the accompanying drawings forming a part hereof, wherein:

Figure 1 is a side elevation partially broken away and in section of the composite gun comprising power unit and magazine assembly secured together in cooperating working relationship;

Fig. 2 is a vertical section taken substantially on the line 22 through the center of the nose piece, air cylinder and piston;

Fig. 3 and Fig. 4 are horizontal sectional details on the lines 3-3 and 4-4 of Fig. 2;

Fig. 5 is a view showing the bottom of the magazine unit and nose piece as seen from the arrow 5 of Fig. 1; and

Fig. 6 is a perspective detail view of the resilient,

bumper carried by the upper end of the staple driver blade.

As shown in the drawings, the numeral 20 indicates generally the main body of the power unit which also serves as a handle by which the operator may grasp and manipulate the stapling gun.

The handle 20 is preferably cored to provide an'expansion chamber 21 into which air under pressure from any suitable source is introduced through a hose 22 connected by a hose nipple 23 to one end of the expansion chamber.

At its other end, the expansion chamber 21 communicates with a valve chamber 24 into which the upper headed end 25a of a valve indicated generally by the reference character 25 projects. At its lower end, valve 25 terminates in a valve stem 25c slidably mounted in a suitable bore 26a of a valve bushing 26 fitted snugly into a bore 28 drilled into the handle 20; bore 28 being closed by a plug 28a screwed into the top thereof, At its lower end, the valve stem 25c terminates in a rounded end 25b adapted to be engaged by a manually operable trigger 27, pivoted as 27a, to the main body or handle portion 20 of the power unit.

The trigger 27 serves to raise the valve seat 251 to an upper opened position in which air from the air source may flow from the valve chamber 24 into the enlarged bore 26b of the bushing 26 and through a combined inlet and exhaust port 260 into a conduit 29, communicating with an annular chamber 30, formed in a boss 35, integral with the handle unit 20 and in which an air cylinder 34 is mounted. The annular chamber 30 communicates through a plurality of longitudinal passageways 31b with a second annular chamber 310 formed in a cylinder closure cap 31, having a screw threaded flange 32 at its lower end for engagement with the screw threads 33 provided at the upper end of the air cylinder 34.

Intermediate its ends the cylinder 34 is provided with an'annular projecting rib 34a that seats within a counter bore 35a formed in the bottom of the boss 35. When the closure cap 31 is screwed onto the threads 33 at the top of cylinder 34, the bottom of the flange 32 of the closure cap 31 will engage the face 350 of a counterbore 35b formed in the top of the boss 35 and will draw the cylinder 34 upwardly to cause the annular rib 34a to be clamped against the bottom face of the counterbore 35a in the lower end of boss 35.

Slidably mounted within the bore of cylinder 34 is a piston 45 which is in the form of a plain cylindrical plug, having a flat upper surface 45a, adapted to engage in contacting sealing engagement with the flat inner face 31a of the cylinder enclosure'cap 31. of the piston is provided around its peripheral edge with an inclined chamfer 45b which serves to facilitate passage of the air under pressure from the annular chamber 31c between the cooperating contacting flat sealing faces The flat face 45a 45a and 31a of the piston 45 and cylinder closure cap 31a, respectively, to break the sealing contact engagement between said surfaces and cause the piston 45 to perform a staple driving stroke. A groove 45c is provided intermediate to the top and bottom ends of the piston to function somewha't'in the nature of a piston ring and to help distribute oil or other suitable lubricant to the contacting surfaces of the piston and cylinder bore.

In addition to the port 26c that provides communication between the bore 26b of the valve bushing 26 and conduit 29, valve bushing 26 is provided with a port 40 that communicates with a conduit 41 formed in the handle and which is open at its rear end to the atmosphere,

The stem of valve has an annular groove 25d which serves to establish communication between the port 260 and port of the valve bushing. The portion25e of the valve stem immediately above the groove 25d is reduced in diameter and serves to form, with the adjacent surface of the upper end of the bore 26a of the bushing 26, a restricted metering opening which serves to retard the flow of air exhausted from the cylinder 34 when the piston 45 is being urged upwardly by the piston return spring 47. The specific constructional details of the valve 25 form no part of the present invention.

The bottom face of the piston 45 engages with the flat upper face of a resilient shock absorbing bumper 46, having an annular flange 46a at its upper end and a downwardly depending cylindrical portion 46b.

The cylindrical portion 46b of the bumper is snugly received within the two uppermost coils 47a of a piston return spring 47; these two coils being substantially in contacting engagement to form, at the upper end of the spring, a substantially cylindrical sheath or sleeve which serves to confine the depending cylindrical portion 46b of the resilient bumper 46 and prevent undue distortion thereof.

At its upper end, the top coil of the spring 47 engages with the under face of the flange 46a of the resilient bumper 46 while at its lower end the coils of. the spring 47 encircle the upper protruding boss 48a of an adapter 48, having a screw threaded annular flange 48b for engagement with lower screw threaded end 50 of the cylinder 34. The adapter 48 is provided with a pair of depending legs 48c slotted, as at 48d, (Fig. 5) to receive cars 61 that project forwardly from the front of the side walls 62a-of the track section 62, to the inner face of the bottom wall 62b of which is welded a staple supporting track 63 that serves to support a strip of interconnected staples 65, adapted to be fed bya staple pusher 66 through a lateral opening 60a provided in the composite nose piece indicated generally at 60 and communicating with a trackway 67, formed in the nose piece and into which the staples 65 are fed.

Slidably mounted in the trackway 67 is the lower end of a staple driver 70, the upper end of which passes through an elongated opening 71, formed in the resilient bumper 46; the driver 70 being provided at its uppermost end with an enlarged head 72 seated within a recess 46c, formed in the upper face of the resilient bumper.

In order to simplify and reduce assembly and manufacturing costs, the nose piece 60 is preferably made as a composite structure which consists of a turned down portion 62c of the bottom wall 62b of the track section, a jamb plate 75, a U-shaped spacer 76 and a pair of guide bars 77. For convenience in assembling the parts 75, 76 and 77, the adapter 48 may be used in effect as an assembly jig for such parts. This is accomplished by broaching a vertical slot 80 (Fig. 5) down through the walls of the boss 48a of the adapter and the inner faces of the depending legs 48c thereof.

The jamb plate 75, the widened lower part 75a (Fig. 5) of which is such width as to fit with a neat sliding fit in said slot is then inserted into the bottom of said slot 80 with the rear face of said jamb plate in abutting engagement with the front face of the downwardly bent leg \ially integral structure.

620 of the bottom wall 62b of the track section 62; the

latter /having first been assembled to the adapter 48 by inserting the ears 61 thereof into the slots 48d in legs 480. At its upper end the jamb plate 75 has a tongue 75b (Fig. 5) which projects upwardly into the channel formed between the side walls of the staple track 63 thereby providing a lateral opening a (Fig. 5) between the ends of side walls 63 and spacer 76 through which the staples are fed from the staple track to the trackway 67. The spacer 76 is slightly (about .003') thicker than the driver blade 70 so that the lower end of the driver blade will fit slidably between the jamb plate 75 and the rear faces of the guide bars 77. The inner edges of the spacer legs are slightly undercut, as at 76b (Fig. 2) in line with the lateral opening 60a to facilitate the passage of the staples into the trackway 77 of the nose piece.

In assembling the component parts of the nose piece, the spacer 76, which for convenience is made as a U- shaped member, as indicated at 76a by the dotted line showing at the bottom of Figs. 1 and 2, is placed in the slot 80 of the adapter in front of the jamb plate 75 and an additional small rectangular guide plate 81 of the same width and thickness as the widened part 75a of the jamb plate is inserted into the top of the slot 80 in the adapter above and in vertical alignment with said jamb plate. After the parts consisting of the adapter 48, track section 62, jamb plate 75, spacer 76, guide bars 77 and plate 81 have all been assembled in the slot 80 of the adapter 48 they are brazed together to form a substan- The portion 76a of the spacer is cut ofi after the parts have been brazed and the lower end of the nose piece assembly is brought to a finished dimension from the top face of the boss 48a such as to define the end of the nose piece in line with the end of the driver blade when it is at the bottom of its stroke.

The front face of the joint plate member 81, together with the front face of the widened part a of the jamb plate 75, form a support for the rear face of the driver blade 70, while the rear faces of the guide bars 77 which extend up through the slot of the adapter to bring their upper edges flush with the top face of boss 48a of the adapter form a support for the front face of the driver blade 70; the top faces of the boss 48a, guide bars 77, and plate 81 forming in effect the top of the composite nose piece 60 against which the bottom of the resilient bumper 46 strikes with shock absorbing contact to limit the downward travel of the piston 45, bumper 46, and staple driver 70 at the end of a staple driving stroke.

At the end of such stroke the mass of resilient material interposed between the enlarged head 72 of the staple driver 70 and the top of the nose piece, effectively cushions said head against the shock of the blow of the bumper against the top of the boss 48a and the composite nose piece 60 and obviates breakage of said head from the top of the driver blade 70.

The manner in which the device operates is similar to the stapling gun disclosed in the prior patent hereinbefore referred to and is as follows: The gun being connected to a source of air under pressure by the hose 22, air is admitted to the valve chamber 24 through conduit 21. During the initial opening movement of valve 26 by trigger 27, the air under pressure in valve chamber flexes the peripheral edge of sealing washer 25f down into sealing contact with the annular sealing surface 26d, then upon continuing to raise the head of the valve 26 by means of the trigger 27 to break the seal between the sealing washer 25f and the annular sealing surface 26d formed on the top face of the bushing 26, the air flows through port 260 of bushing 26 through conduit 29 to annular chamber 30, thence through longitudinal passages 31!) into the annular chamber 310 of the cylinder closure cap 31; the air under pressure entering between the flat contacting surfaces 31a and 45a of the cylinder closure cap and piston 45 respectively to break the sealing engagement thereof; the chamfer 45b facilitating such entry. The piston is piston moves downwardly, the under surface thereof.

which contacts directly with the enlarged head 72 of the driver 70, also causes the driver to perform a staple driving stroke. At the same timmthe resilient bumper 46 is forced downwardly by the piston and compresses the piston return spring 47 until. the lower end of the driver reaches the bottom face of the nose piece at which time the lower face of the cylindrical portion of 46b of the bumper engages with a resilient shock absorbing contact with the top face of the boss 48a of the adapter 48 of the nose piece. When such contact occurs the sheath or sleeve, formed by the two top coils 47a of the piston spring 47 that encircles the depending portion 46b of the bumper preventsundue distortion thereof. The spring 47 by reason of its engagement with the flange 46a of the bumper 46 then immediately forces the bumper 46, staple driver 70 and piston 45 upwardly, the air in the cylinder 34 above the piston 45 being exhausted through annular chamber 310, longitudinalpassageways 31b, annular chamber 30 and conduit 29 to port 260, valve groove 25d and port 40 to conduit 41 to the atmosphere; the-restricted metering opening between the reduced portion 25a of valve 25 and bore 26a of bushing 26 serving to retard the exhaust flow of the air and thereby cushioning the shock of the contact of the piston 45 against the inner face 31a of the cylinder closure cap 31. Spring 47 then holds the flat face 45a of piston 45 in contacting sealing c iindrical piston having flat upper and lower surfaces sgldably mounted therein, a cylinder closure cap engaged with the threaded upper end of said cylinder, a coiled compression spring for normally holding said piston in engagement with said closure cap, a staple driver having an enlarged upper end in simple contacting engagement. with the lower face of said piston, a nose piece having a trackway into which staples to be driven are fed one by one, the lower end of said driver being slidably mounted in the trackway of said nose piece, valve means for admitting air from a source of air under pressure into said cylinder between said piston and said closure cap to cause said piston and driver toperform a staple driving stroke,- and a resilient shock absoi'bing bumper having a flat upper surface in simple contactiiige engagement with the lower surface of said piston, interposed between said piston and nose piece for shock absorbing engagement with said nose piece to stop the travel of said piston when it reaches the end of its driving stroke.

engagement with the flat inner face 31a of the cylinder t closure cap 31 until the trigger 27 is again actuated to move the valve 25 to its fully opened position to cause the piston and staple driver blade to perform another staple driving stroke. a

It will be noted that the outer diameter of the coiled piston return spring 47 is such that the spring fits slidably within the bore of the cylinder 34 so that the latter, togetherwith the'engagement of the boss 48a of the adapter 48 and the depending cylindrical portion 46b of the bumper with the inner faces of the bottom and top coils respectively of the spring 47 serve to keep the spring coils in proper vertical alignment.

While we havedescribed and illustrated a highly satisfactory constructional example of our invention it will of course be understood that many changes, variations and modifications thereof may be resorted to without departing from the spirit of the invention as covered by the scope of the claims hereunto appended.

We claim:

1. In an air gun for driving fastening devices such as staples, tacks, brads or the like, an air cylinder, a piston slidably mounted in said cylinder, a driver having an enlarged headed end in simple contacting engagement with said piston for engaging the fastening devices to be driven, a nose piece in which the lower end of said driver is slidably mounted, valve means for admitting air from a source of air under pressure to said cylinder to'cause said piston and driver to perform a driving stroke, a coiled compression piston spring for normally urging said piston toward the top of said cylinder, and a resilient shock absorbing bumper in contacting engagement with said piston and the enlarged head of said driver and interposed between said nose piece and said piston and the enlarged head of said driver for contacting shock absorbing engagement with said nose piece to stop the travel of said piston and driver at the lower end of said cylinder.

2. A pneumatic stapling gun according to claim 1 in which said bumper is interposed between said piston and said piston spring and is provided on its upper face with a recess in which the enlarged head of said driver is received whereby said piston spring serves to urge said bumper, said driver and said piston in unison to the top of said cylinder after the end of a driving stroke.

3. In a pneumatic staple driving gun, an air cylinder having screw threaded upper and lower ends, a plain 4. A pneumatic staple driving gun according to claim 3 in which the upper terminal coils of said spring are in substantially contacting engagement with each other to form a sleeve like receptacle and said bumper has a depending cylindricalportiomsnuglyrogfined within said sleeve like receptacle to prevent undue distortiorfihercofl when said bumper strikes said nose piece.

5. A pneumatic staple driving gun according to claim 4 in which said resilient bumper is provided with a central passageway through which said driver passes.

6. A pneumatic staple driving gun according to claim 3 in which the upper face of said resilient bumper is recessed to receive the enlarged upper end of said driver.

7. A pneumatic staple driving gun according to claim 3 in which said resilient bumper has a projecting annular flange at its upper edge and a cylindrical portion depending therefrom, said flange being in abutting engagement with the top end coil of said spring to receive the thrust of said spring and the uppermost coils of said spring snugly encircling said depending cylindrical portion of said bumper and serving to limit distortion thereof.

8. A pneumatic staple driving gun according to claim 3 in which a screw threaded adapter, detachably engaged with the screw threaded lower end of said cylinder is provided with a central boss projecting, upwardly into said cylinder and a central rectangular slot, and a plurality of flat guide plate elements having spacing means interposed between their juxtaposed flat faces mounted within said slot and united to each other and to said adapter by fused joints to form said nose piece and said trackway thereof as a substantially composite integral structure with said adapter in which said lower end of said driver is slidably mounted, and in which said guide elements provide flat guiding surfaces for said driver.

9. A pneumatic staple driving gun according to claim 3 in which said nose piece is formed by a screw threaded adapter, secured within the lower threaded end of said cylinder, and provided with a central boss projecting upwardly into said cylinder, a pair of laterally spaced side guide bars having their upper ends flush with the top of said boss and-their lower ends projecting below said cylinder, a jamb plate and spacing means are integrally united with said adapter to form the trackway of said nose piece in which the lower end of said staple driver is slidably received and into which the staples are fed below said driver to be driven thereby into the material to be stapled.

10. A pneumatic stapling gun as set forth in claim 9 in which said adapter is provided with a pair of slotted depending legs-in the slots of which, ears projecting forwardly from the side walls of a staple magazine track section are received and a joint of fused material between said legs and said ears unites said track section tosaid adapter to form an integral structure therewith.

11-. A pneumatic stapling gun as set forth in claim 9 in which a guide plate is mounted within the top of said boss in vertical alignment with said iamb plate to form therewith a guiding and supporting surface for the rear face of said staple driver.

12. A pneumatic staple driving gun according to claim 9 in which an inverted U-shaped staple carrying track has its front end integrally united with said adapter and said jamb plate has a reduced tongue projecting upwardly between and spaced from the walls of said track to define a lateral opening communicating with the' trackway of said nose piece through which staples carried by said track may be fed into said tracltway below said driver to be driven thereby into the material to be stapled.

13. A pneumatic stapling gun as set forth in claim 12 in which the inner side edgesof said spacing means are slightly cut away in'line with said lateral opening to facilitate passage of the staples into the tracltway of said nose piece.

14. A pneumatic stapling gun as set forth in claim 12 in which staple feeding means is slidably mounted on said staple carrying track to cause the staples thereon to be fed through said lateral opening into the trackway of said nose piece below said driver to be driven thereby into the material to be stapled.

15. An air gun for driving fastening devices such as staples, tacks, brads or the like, having a cylinder, a piston, a driver, a closure member at one end of said cylinder slidably supporting said driver for movement relative to said cylinder, a return spring for normally urging said piston toward the head end of said cylinder, and means foradmittingairfromasourceofairpr'essuretothe head end of said cylinder, characterized by the provision of a resilient shock absorbing bumper interposed between said piston and said return spring, and means connecting said bumper and said driver whereby said driver is urged toward the head end of said cylinder with said bumper and piston by said return spring.

References Cited in the file of this patent STATES PATENTS 

